title: High-level expression of a functional humanized anti-CTLA4 single-chain variable fragment antibody in Pichia pastoris.
abstract: The administration of antibodies against the cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is a promising approach in the upregulation of immune responses in many cancers and infectious diseases. The single-chain variable fragment of antibody against CTLA4 is also useful in developing immunotoxins that might be used in the treatment of cancer, transplant rejection, and autoimmune diseases. Here, we report the production of a soluble and functional scFv antibody against CTLA4 by using Pichia pastoris as the expression system. The gene encoding scFv hS83 with an additional 6His-tag at the 5'-end was inserted into the expression vector pPIC9K. Then, the transformants were double-screened on plates containing 0.25 mg/mL and 1.5 mg/mL of neomycin G418 and many clones with different levels of G418-resistance were selected for further studies on expression. After induction by the addition of methanol, various levels of hS83 were detected in the supernatant of P. pastoris containing pPIC9K-hS83. Clones with low G418-resistance produced more hS83 than those with higher G418-resistance. Under the optimized conditions (initial inoculum, 40 A(600nm) AU/mL; pH 6.0; methanol concentration, 3.0%; induction time, 72 h), approximately 16-20 mg protein could be recovered from 1 L of the culture. The purified hS83 had a stronger binding ability towards CTLA4-positive Raji cells than CTLA4-negative ECV304 cells. This finding indicates that the antibody produced by P. pastoris is functional and may be used in immunotherapy for cancer, infection, transplant rejection, and autoimmune diseases.
authors.affiliation: Key laboratory of Transplant Engineering and Immunology, West China Hospital, Sichuan University, Chengdu, 610041, China.
authors.forename: Huawei
authors.initials: H
authors.lastname: Cai
authors.forename: Lihong
authors.initials: L
authors.lastname: Chen
authors.forename: Lin
authors.initials: L
authors.lastname: Wan
authors.forename: Lingyu
authors.initials: L
authors.lastname: Zeng
authors.forename: Hao
authors.initials: H
authors.lastname: Yang
authors.forename: Shengfu
authors.initials: S
authors.lastname: Li
authors.forename: Youping
authors.initials: Y
authors.lastname: Li
authors.forename: Jingqiu
authors.initials: J
authors.lastname: Cheng
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Lu
mesh_terms: D000906:Antibodies / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D015703:Antigens, CD / Q000276:immunology*; D060908:CTLA-4 Antigen; D002460:Cell Line; D003001:Cloning, Molecular; D015870:Gene Expression; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D000922:Immunotoxins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D010843:Pichia / Q000235:genetics* / Q000378:metabolism; D015202:Protein Engineering
chemical_list: D000906:Antibodies; D015703:Antigens, CD; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D007135:Immunoglobulin Variable Region; D000922:Immunotoxins